YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.

Multiple Vulnerabilities in YAML Syck

The remote Debian 13 host has a package installed that is affected by multiple vulnerabilities as referenced in the dsa-6428 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6428-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     August 10, 2026                       https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : libyaml-syck-perl     CVE ID         : CVE-2026-5089 CVE-2026-13713 CVE-2026-57075 CVE-2026-57076                      CVE-2026-57077     Debian Bug     : 1142267

    Several vulnerabilities were discovered in libyaml-syck-perl, a Perl     module providing a fast, lightweight YAML loader and dumper, which could     result in denial of service and potentially arbitrary code execution.

    For the stable distribution (trixie), these problems have been fixed in     version 1.34-2+deb13u3.

    We recommend that you upgrade your libyaml-syck-perl packages.

    For the detailed security status of libyaml-syck-perl please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/libyaml-syck-perl

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Debian 11 / 12 host has a package installed that is affected by multiple vulnerabilities as referenced in the dla-4730 advisory.

    - -------------------------------------------------------------------------     Debian LTS Advisory DLA-4730-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                 Salvatore Bonaccorso     August 10, 2026                               https://wiki.debian.org/LTS
    - -------------------------------------------------------------------------

    Package        : libyaml-syck-perl     Version        : 1.34-1+deb11u2 1.34-2+deb12u3     CVE ID         : CVE-2026-5089 CVE-2026-13713 CVE-2026-57075 CVE-2026-57076                      CVE-2026-57077     Debian Bug     : 1142267

    Several vulnerabilities were discovered in libyaml-syck-perl, a Perl     module providing a fast, lightweight YAML loader and dumper, which could     result in denial of service and potentially arbitrary code execution.

    For Debian 11 bullseye, these problems have been fixed in version     1.34-1+deb11u2.

    For Debian 12 bookworm, these problems have been fixed in version     1.34-2+deb12u3.

    We recommend that you upgrade your libyaml-syck-perl packages.

    For the detailed security status of libyaml-syck-perl please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/libyaml-syck-perl

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of perl-YAML-Syck installed on the remote host is prior to 1.27-3. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3837 advisory.

    YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed     while still on the parser value stack.

    In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and     syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be     live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a     normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special     flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor     triggers it.

    Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes     the interpreter, a denial of service. (CVE-2026-13713)

    YAML::Syck versions before 1.47 for Perl allow an out-of-bounds read via a signed-char lookup-table index     in syck_base64dec.

    The base64 decoder in the bundled libsyck indexes the 256-entry static table b64_xtable with a signed     char, so any !!binary byte >= 0x80 sign-extends to a negative index and reads before the table. The     decoder receives the raw bytes of any !!binary node, a standard YAML type not gated by $LoadBlessed or     $LoadCode, so it is reached on the default Load path.

    Any caller that runs Load or LoadFile on an untrusted document containing a !!binary scalar with a high-     bit byte triggers the read, and the value read can surface in the decoded result. (CVE-2026-57075)

    YAML::Syck versions before 1.47 for Perl allow a heap use-after-free via an anchor name reused as an     anchors-table key in syck_hdlr_add_anchor.

    In the bundled libsyck an anchor name allocated by syck_strndup is stored both as node->anchor, freed when     the node is freed, and as the key in the parser's anchors table. Freeing the node frees the shared key,     and a later anchor redefinition makes st_delete compare against the freed key, so st_strcmp reads freed     heap memory. Anchors are a standard YAML feature and need no special flags, so this is reached on the     default Load path.

    Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor reaches the read     of freed memory. (CVE-2026-57076)

    YAML::Syck versions before 1.47 for Perl allow an out-of-bounds read via an unbounded newline scan in     newline_len.

    In the bundled libsyck newline_len and is_newline dereference the scan pointer, and the following byte for     a \r\n pair, with no NUL-terminator or bounds check. During block-scalar lexing at a document boundary     the scan runs one byte past the heap lexer buffer. This is an incomplete fix of CVE-2025-11683, on a lexer     path the earlier fix did not cover.

    Any caller that runs Load or LoadFile on an untrusted document with a block scalar at a document boundary     reaches the over-read. (CVE-2026-57077)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2007 advisory.

    YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed     while still on the parser value stack.

    In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and     syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be     live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a     normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special     flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor     triggers it.

    Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes     the interpreter, a denial of service. (CVE-2026-13713)

    YAML::Syck versions before 1.47 for Perl allow an out-of-bounds read via a signed-char lookup-table index     in syck_base64dec.

    The base64 decoder in the bundled libsyck indexes the 256-entry static table b64_xtable with a signed     char, so any !!binary byte >= 0x80 sign-extends to a negative index and reads before the table. The     decoder receives the raw bytes of any !!binary node, a standard YAML type not gated by $LoadBlessed or     $LoadCode, so it is reached on the default Load path.

    Any caller that runs Load or LoadFile on an untrusted document containing a !!binary scalar with a high-     bit byte triggers the read, and the value read can surface in the decoded result. (CVE-2026-57075)

    YAML::Syck versions before 1.47 for Perl allow a heap use-after-free via an anchor name reused as an     anchors-table key in syck_hdlr_add_anchor.

    In the bundled libsyck an anchor name allocated by syck_strndup is stored both as node->anchor, freed when     the node is freed, and as the key in the parser's anchors table. Freeing the node frees the shared key,     and a later anchor redefinition makes st_delete compare against the freed key, so st_strcmp reads freed     heap memory. Anchors are a standard YAML feature and need no special flags, so this is reached on the     default Load path.

    Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor reaches the read     of freed memory. (CVE-2026-57076)

    YAML::Syck versions before 1.47 for Perl allow an out-of-bounds read via an unbounded newline scan in     newline_len.

    In the bundled libsyck newline_len and is_newline dereference the scan pointer, and the following byte for     a \r\n pair, with no NUL-terminator or bounds check. During block-scalar lexing at a document boundary     the scan runs one byte past the heap lexer buffer. This is an incomplete fix of CVE-2025-11683, on a lexer     path the earlier fix did not cover.

    Any caller that runs Load or LoadFile on an untrusted document with a block scalar at a document boundary     reaches the over-read. (CVE-2026-57077)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote openSUSE 16 host has a package installed that is affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:21497-1 advisory.

    Changes in perl-YAML-Syck:

    - updated to 1.470.0 (1.47)         [Security]
        - Fix four libsyck memory-safety CVEs reachable from the default           YAML::Syck::Load() path on untrusted input with no special flags           (reported by Paul Johnson via CPANSec, PR #213):
          - CVE-2026-57075 (CWE-125): out-of-bounds read in the base64 decoder             caused by signed-char indexing of the decode table on !!binary input             bsc#1271632
          - CVE-2026-57076 (CWE-416): use-after-free of an anchor key string             shared between the node and the anchors table             bsc#1271633
          - CVE-2026-57077 (CWE-125): one-byte out-of-bounds read in the lexer             newline scan during block-scalar parsing (incomplete-fix follow-on             to CVE-2025-11683)             bsc#1271634
          - CVE-2026-13713 (CWE-416/CWE-415): use-after-free / double-free of an             anchor node on anchor redefinition, a remote-crash DoS from a             7-byte input             bsc#1271631
        - Harden syck_base64dec() to bounds-check each read so it cannot run past           a non-NUL-terminated input buffer (defense-in-depth for callers passing           raw buffers; PR #213)         [Bug Fixes]
        - Fix: enforce $MaxDepth on Load to prevent C-stack exhaustion from           deeply nested YAML/JSON input; YAML::Syck and JSON::Syck Load now           default to 512, matching Dump (PR #204)
        - Fix: emit YAML canonical forms (.nan, .inf, -.inf) for NaN/Inf values           in Dump so they roundtrip with ImplicitTyping instead of reloading as           plain strings (PR #201)         [Maintenance]
        - CI: add an AddressSanitizer job that builds the XS with
          -fsanitize=address and runs the suite plus the CVE trigger inputs to           catch libsyck memory-safety defects; de-pin the libasan version so it           tracks the runner's GCC (PR #213)

    - updated to 1.460.0 (1.46)         [Bug Fixes]
        - Fix: preserve string nature of numeric-looking values in Dump; pure           strings (POK only, no IOK/NOK) are now quoted to maintain roundtrip           fidelity (GH #199, PR #200)
        - Fix: accept trailing commas in flow sequences and mappings           ([a, b,] and {a: 1,}), valid per YAML 1.0/1.1/1.2 spec           (GH #195, PR #196)

        [Maintenance]
        - CI: upgrade install-with-cpm to v2 for compatibility with Perl           versions prior to 5.24 in perldocker containers (GH #197, PR #198)
        - Clean up MANIFEST.SKIP: add #!include_default, remove redundant           entries, exclude .claude/ from distribution

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote openSUSE 16 host has a package installed that is affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:21452-1 advisory.

    Changes in perl-YAML-Syck:

    - updated to 1.470.0 (1.47)         [Security]
        - Fix four libsyck memory-safety CVEs reachable from the default           YAML::Syck::Load() path on untrusted input with no special flags           (reported by Paul Johnson via CPANSec, PR #213):
          - CVE-2026-57075 (CWE-125): out-of-bounds read in the base64 decoder             caused by signed-char indexing of the decode table on !!binary input             bsc#1271632
          - CVE-2026-57076 (CWE-416): use-after-free of an anchor key string             shared between the node and the anchors table             bsc#1271633
          - CVE-2026-57077 (CWE-125): one-byte out-of-bounds read in the lexer             newline scan during block-scalar parsing (incomplete-fix follow-on             to CVE-2025-11683)             bsc#1271634
          - CVE-2026-13713 (CWE-416/CWE-415): use-after-free / double-free of an             anchor node on anchor redefinition, a remote-crash DoS from a             7-byte input             bsc#1271631
        - Harden syck_base64dec() to bounds-check each read so it cannot run past           a non-NUL-terminated input buffer (defense-in-depth for callers passing           raw buffers; PR #213)         [Bug Fixes]
        - Fix: enforce $MaxDepth on Load to prevent C-stack exhaustion from           deeply nested YAML/JSON input; YAML::Syck and JSON::Syck Load now           default to 512, matching Dump (PR #204)
        - Fix: emit YAML canonical forms (.nan, .inf, -.inf) for NaN/Inf values           in Dump so they roundtrip with ImplicitTyping instead of reloading as           plain strings (PR #201)         [Maintenance]
        - CI: add an AddressSanitizer job that builds the XS with
          -fsanitize=address and runs the suite plus the CVE trigger inputs to           catch libsyck memory-safety defects; de-pin the libasan version so it           tracks the runner's GCC (PR #213)

    - updated to 1.460.0 (1.46)         [Bug Fixes]
        - Fix: preserve string nature of numeric-looking values in Dump; pure           strings (POK only, no IOK/NOK) are now quoted to maintain roundtrip           fidelity (GH #199, PR #200)
        - Fix: accept trailing commas in flow sequences and mappings           ([a, b,] and {a: 1,}), valid per YAML 1.0/1.1/1.2 spec           (GH #195, PR #196)

        [Maintenance]
        - CI: upgrade install-with-cpm to v2 for compatibility with Perl           versions prior to 5.24 in perldocker containers (GH #197, PR #198)
        - Clean up MANIFEST.SKIP: add #!include_default, remove redundant           entries, exclude .claude/ from distribution

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 44 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-2139aa7dce advisory.

     This update addresses four `libsyck` memory-safety CVEs reachable from the default `YAML::Syck::Load()`     path on untrusted input with no special flags:

     * CVE-2026-57075 (CWE-125): Out-of-bounds read in the base64 decoder caused by signed-char indexing of     the decode table on !!binary input
     * CVE-2026-57076 (CWE-416): Use-after-free of an anchor key string shared between the node and the     anchors table
     * CVE-2026-57077 (CWE-125): One-byte out-of-bounds read in the lexer newline scan during block-scalar     parsing (incomplete-fix follow-on to CVE-2025-11683)
     * CVE-2026-13713 (CWE-416/CWE-415): Use-after-free / double-free of an anchor node on anchor     redefinition, a remote-crash DoS from a 7-byte input

    There are also a few other bug-fixes included.


Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-c8484f1afb advisory.

     This update addresses four `libsyck` memory-safety CVEs reachable from the default `YAML::Syck::Load()`     path on untrusted input with no special flags:

     * CVE-2026-57075 (CWE-125): Out-of-bounds read in the base64 decoder caused by signed-char indexing of     the decode table on !!binary input
     * CVE-2026-57076 (CWE-416): Use-after-free of an anchor key string shared between the node and the     anchors table
     * CVE-2026-57077 (CWE-125): One-byte out-of-bounds read in the lexer newline scan during block-scalar     parsing (incomplete-fix follow-on to CVE-2025-11683)
     * CVE-2026-13713 (CWE-416/CWE-415): Use-after-free / double-free of an anchor node on anchor     redefinition, a remote-crash DoS from a 7-byte input

    There are also a few other bug-fixes included.


Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed     while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or     removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with     syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it     again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the     interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a     7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an     untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.
    (CVE-2026-13713)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
334412	Debian dsa-6428 : libyaml-syck-perl - security update	Nessus	Debian Local Security Checks	critical
334411	Debian dla-4730 : libyaml-syck-perl - security update	Nessus	Debian Local Security Checks	critical
331999	Amazon Linux 2 : perl-YAML-Syck, --advisory ALAS2-2026-3837 (ALAS-2026-3837)	Nessus	Amazon Linux Local Security Checks	critical
331983	Amazon Linux 2023 : perl-YAML-Syck, perl-YAML-Syck-tests (ALAS2023-2026-2007)	Nessus	Amazon Linux Local Security Checks	critical
331560	openSUSE 16 Security Update : perl-YAML-Syck (openSUSE-SU-2026:21497-1)	Nessus	SuSE Local Security Checks	critical
330582	openSUSE 16 Security Update : perl-YAML-Syck (openSUSE-SU-2026:21452-1)	Nessus	SuSE Local Security Checks	critical
329164	Fedora 44 : perl-YAML-Syck (2026-2139aa7dce)	Nessus	Fedora Local Security Checks	critical
329162	Fedora 43 : perl-YAML-Syck (2026-c8484f1afb)	Nessus	Fedora Local Security Checks	critical
327541	Linux Distros Unpatched Vulnerability : CVE-2026-13713	Nessus	Misc.	medium

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