A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream, the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2 server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort the process or fail the HTTP/2 session.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream,
    the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2
    server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client
    then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort
    the process or fail the HTTP/2 session. (CVE-2026-85534)

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8890-1 advisory.

    It was discovered that libsoup incorrectly handled certain HTTP/2 requests. A remote attacker could     possibly use this issue to cause a denial of service. This issue only affected Ubuntu 24.04 LTS and Ubuntu     26.04 LTS. (CVE-2026-4271)

    It was discovered that libsoup incorrectly handled certain HTTPS proxy connections. A remote attacker     could possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 22.04 LTS,     Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-5119)

    It was discovered that libsoup incorrectly parsed certain chunked HTTP requests. A remote attacker could     possibly use this issue to bypass security controls. This issue only affected Ubuntu 22.04 LTS, Ubuntu     24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-6324)

    It was discovered that libsoup incorrectly handled proxy authentication credentials. A remote attacker     could possibly use this issue to obtain sensitive information. (CVE-2026-66339)

    It was discovered that libsoup incorrectly handled certain HTTP Range headers. A remote attacker could     possibly use this issue to cause a denial of service. (CVE-2026-77014, CVE-2026-77680)

    It was discovered that libsoup incorrectly handled certain HTTP/2 connections. A remote attacker could     possibly use this issue to obtain sensitive information or execute arbitrary code. This issue only     affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-85197)

    It was discovered that libsoup incorrectly handled certain HTTP/2 transfers. A remote attacker could     possibly use this issue to cause a denial of service. This issue only affected Ubuntu 22.04 LTS, Ubuntu     24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-85534)

Tenable has extracted the preceding description block directly from the Ubuntu 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 ALAS2023-2026-3144 advisory.

    The fix for CVE-2026-0716 (commit 6ff7ef0, libsoup 3.6.6) placed the integer overflow guard inside the if     (masked) block, leaving unmasked server-to-client frames unprotected. A malicious WebSocket server can     send a crafted unmasked frame with a payload length near UINT64_MAX to trigger an OOB read in a libsoup-     based client when max_incoming_payload_size is set to 0. (CVE-2026-12478)

    SoupAuthManager caches proxy authentication credentials without scoping them to the proxy authority     (host:port). When the proxy configuration changes (e.g., via system settings or WPAD), cached Proxy-     Authorization headers from the previous proxy are sent to the new proxy, leaking credentials.
    (CVE-2026-12547)

    A heap out-of-bounds read flaw was found in libsoup. When parsing multipart HTTP messages, an integer type     mismatch between the caller and soup_headers_parse() can cause the length parameter to be incorrectly     truncated, leading to a heap buffer over-read. A remote attacker could use this flaw to crash an     application using libsoup or potentially disclose heap memory contents. (CVE-2026-12548)

    The fix for CVE-2026-2443 was regressed by a subsequent rework commit that replaced specific overflow     checks with a general signed comparison. When a client sends a Range request with a suffix length     exceeding the content size, the resulting negative start value is not properly clamped, leading to     malformed HTTP 206 responses and log flooding. (CVE-2026-12549)

    A heap buffer over-read vulnerability was discovered in libsoup's HTTP/2 connection tracking framework.
    When the library processes an HTTP/2 GOAWAY frame, it improperly handles the Additional Debug Data     payload by assuming the data stream is a safely NUL-terminated C-string. Because the parser lacks strict     length-boundary verification before reading this data, a remote, unauthenticated attacker can     intentionally send a malformed GOAWAY frame missing the appropriate null delimiter. This causes the     library to read past the end of the allocated buffer, triggering an application crash that results in a     denial of service (DoS), or potentially exposing fragments of memory contents. (CVE-2026-15712)

    A vulnerability was found in libsoup's HTTP/2 protocol implementation. The library fails to correctly     release memory context blocks under specific stream termination conditions, such as when an HTTP/2     connection encounters window exhaustion or explicit stream resets. A remote, unauthenticated attacker     acting as a malicious network peer can trick the connection engine into allocating stream states that are     subsequently leaked during cleanup. Over a sustained period, this flaw allows the remote attacker to     consume the system's heap allocations incrementally, triggering a denial of service (DoS) through an     ultimate Out-of-Memory (OOM) application crash. (CVE-2026-15713)

    An out-of-bounds read vulnerability was found in libsoup's multipart processing subsystem. The flaw exists     in the soup_multipart_input_stream_read_headers() function inside soup-multipart-input-stream.c, which     does not adequately restrict or validate the size of incoming multipart boundary strings. When processing     a crafted HTTP response containing a malformed or oversized boundary parameter, the internal stream reader     reads past the allocated buffer bounds. A remote, unauthenticated attacker can exploit this behavior to     cause a service denial (DoS) through application failure or potentially read fragments of unauthorized     memory metadata. (CVE-2026-15714)

    A flaw was found in libsoup. After a CONNECT tunnel is established through an HTTP proxy, libsoup     incorrectly attaches the Proxy-Authorization header to subsequent HTTPS requests sent through that tunnel     to the destination server. This allows the destination server to capture proxy credentials, leading to     information disclosure. (CVE-2026-66339)

    A flaw was found in libsoup's SoupServer HTTP Range header processing. The sort_ranges() comparator in     soup-message-headers.c truncates a 64-bit subtraction result to 32-bit int, flipping the sign for range     offsets differing by more than INT_MAX. This causes silent omission of requested byte ranges from HTTP 206     Partial Content responses on resources larger than approximately 2 GB. (CVE-2026-77014)

    An algorithmic complexity flaw exists in libsoup's HTTP Range header processing that persists after the     CVE-2025-32907 fix.

    CVE-2025-32907 addressed memory amplification when a client repeated the same range many times in a single     Range header. Commit 9bb92f7a corrected merge correctness in soup_message_headers_get_ranges_internal() in     libsoup/soup-message-headers.c, but the coalescing loop still removes merged ranges using     g_array_remove_index() for each coalesced element. Because GArray is contiguous, each mid-array removal     performs an O(N) memmove. When many identical satisfiable ranges are supplied (for example bytes=0-0     repeated thousands of times), the loop performs O(N2) work coalescing them into a single range.

    The vulnerable path is reachable server-side from handle_partial_get() in libsoup/server/http1/soup-     server-message-io-http1.c when a SoupServer handler returns HTTP 200 with a non-empty body. No     authentication is required. The number of ranges is bounded only by the maximum request header size (~100     KiB), allowing roughly 25,000 ranges per request. Reporter measurements on libsoup HEAD containing the     CVE-2025-32907 fix show ~90 ms single-core CPU per such request at the wire maximum, blocking the server's     event loop for that duration.

    This is a CPU exhaustion / availability issue only. No memory corruption or information disclosure occurs.

    Affected: libsoup versions containing the CVE-2025-32907 fix but not merge request !550.Fixed upstream: MR     !550 merged 2026-08-20, replacing per-element removal with O(N) in-place compaction and rejecting Range     headers requesting more than 200 ranges.Upstream report:
    https://gitlab.gnome.org/GNOME/libsoup/-/issues/538Related: CVE-2025-32907 (CVE-2026-77680)

    A flaw was found in libsoup. A malicious HTTP/2 server or a Man-in-the-Middle (MITM) attacker can exploit     a heap use-after-free vulnerability in the HTTP/2 client implementation. This occurs when a GNOME     application uploads a file using HTTP/2, and the server sends a GOAWAY frame while the file body is being     read asynchronously. This can lead to memory corruption, potentially resulting in information disclosure     or arbitrary code execution. (CVE-2026-85197)

    A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream,     the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2     server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client     then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort     the process or fail the HTTP/2 session. (CVE-2026-85534)

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 SUSE Linux SLES16 / SLES_SAP16 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:23857-1 advisory.

    - CVE-2026-85197: heap use-after-free in HTTP/2 `client on_data_read()` via `GOAWAY` during body upload     (bsc#1279238).
    - CVE-2026-85534: heap buffer overflow in `SoupSession` through `on_data_source_read_callback()` via     `SETTINGS` frame       with crafted `INITIAL_WINDOW_SIZE` (bsc#1279239).

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 packages installed that are affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:21901-1 advisory.

    - CVE-2026-85197: heap use-after-free in HTTP/2 `client on_data_read()` via `GOAWAY` during body upload     (bsc#1279238).
    - CVE-2026-85534: heap buffer overflow in `SoupSession` through `on_data_source_read_callback()` via     `SETTINGS` frame       with crafted `INITIAL_WINDOW_SIZE` (bsc#1279239).

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 SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:4273-1 advisory.

    - CVE-2026-85197: heap use-after-free in HTTP/2 `client on_data_read()` via `GOAWAY` during body upload     (bsc#1279238).
    - CVE-2026-85534: heap buffer overflow in `SoupSession` through `on_data_source_read_callback()` via     `SETTINGS` frame       with crafted `INITIAL_WINDOW_SIZE` (bsc#1279239).

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 SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:4274-1 advisory.

    - CVE-2026-85197: heap use-after-free in HTTP/2 `client on_data_read()` via `GOAWAY` during body upload     (bsc#1279238).
    - CVE-2026-85534: heap buffer overflow in `SoupSession` through `on_data_source_read_callback()` via     `SETTINGS` frame       with crafted `INITIAL_WINDOW_SIZE` (bsc#1279239).

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

  - A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream,     the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2     server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client     then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort     the process or fail the HTTP/2 session. (CVE-2026-85534)

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

ID	Name	Product	Family	Type	Severity
473740	Echo: libsoup3: security update to 3.6.6-1+e12	Tenable Cloud Security	Echo Local Security Checks	Local	medium
473740	Echo: libsoup3: security update to 3.6.6-1+e12	Tenable Self-Hosted Container Security	Echo Local Security Checks	Local	medium
363740	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS : libsoup vulnerabilities (USN-8890-1)	Nessus	Ubuntu Local Security Checks	Local	high
351071	Amazon Linux 2023 : libsoup3, libsoup3-devel (ALAS2023-2026-3144)	Nessus	Amazon Linux Local Security Checks	Local	high
350828	SUSE SLES16 Security Update : libsoup (SUSE-SU-2026:23857-1)	Nessus	SuSE Local Security Checks	Local	high
350158	openSUSE 16 Security Update : libsoup (openSUSE-SU-2026:21901-1)	Nessus	SuSE Local Security Checks	Local	high
348730	SUSE SLED15 / SLES15 Security Update : libsoup (SUSE-SU-2026:4273-1)	Nessus	SuSE Local Security Checks	Local	high
348724	SUSE SLES15 Security Update : libsoup (SUSE-SU-2026:4274-1)	Nessus	SuSE Local Security Checks	Local	high
342820	Linux Distros Unpatched Vulnerability : CVE-2026-85534	Nessus	Misc.	Local	medium

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