Detections
Analytics
TencentOS Server 4: python-jwt (TSSA-2026:0427)
medium Nessus Plugin ID 319736
Synopsis
The remote TencentOS Server 4 host is missing one or more security updates.Description
The version of Tencent Linux installed on the remote TencentOS Server 4 host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0427 advisory.Package updates are available for TencentOS Server 4 that fix the following vulnerabilities:
CVE-2026-48525:
PyJWT is a JSON Web Token implementation in Python. From 2.8.0 to 2.12.1, when verifying detached JWS tokens using the unencoded-payload option (b64: false, RFC 7797), PyJWT performs Base64URL decoding of the compact-serialization payload segment before enforcing the detached-payload rules. For b64=false, PyJWT later discards that decoded payload and replaces it with the caller-provided detached_payload. In practice, this turns the middle segment into an attacker-controlled work amplifier: a remote client can supply an arbitrarily large Base64URL payload segment that forces CPU work + memory allocations even if the signature is invalid. This creates an unauthenticated DoS vector against any endpoint that verifies detached JWS using PyJWT. This vulnerability is fixed in 2.13.0.
CVE-2026-48524:
PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting.
Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests. The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker's control. This vulnerability is fixed in 2.13.0.
CVE-2026-48523:
PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.
CVE-2026-48522:
PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib's default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch. If an application's jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem), cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface), or forge tokens that PyJWT verifies as valid. The library does not directly return non-HTTP(S) URI contents to the attacker; the chained 'plant a JWKS to forge tokens' scenario described in the original report requires additional application- layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. This vulnerability is fixed in 2.13.0.
Tenable has extracted the preceding description block directly from the Tencent Linux security advisory.
Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.
Solution
Update the affected packages.See Also
Plugin Details
Severity: Medium
ID: 319736
File Name: tencentos_TSSA_2026_0427.nasl
Version: 1.1
Type: Local
Family: Tencent Local Security Checks
Published: 6/8/2026
Updated: 6/8/2026
Supported Sensors: Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 4.0
CVSS v2
Risk Factor: Medium
Base Score: 5.5
Temporal Score: 4.3
Vector: CVSS2#AV:N/AC:L/Au:S/C:P/I:P/A:N
CVSS Score Source: CVE-2026-48523
CVSS v3
Risk Factor: Medium
Base Score: 5.4
Temporal Score: 4.9
Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C
Vulnerability Information
CPE: p-cpe:/a:tencent:tencentos_server:python-jwt, cpe:/o:tencent:tencentos_server:4
Required KB Items: Host/local_checks_enabled, Host/cpu, Host/etc/os-release, Host/TencentOS/rpm-list
Exploit Available: true
Exploit Ease: Exploits are available
Patch Publication Date: 6/4/2026
Vulnerability Publication Date: 5/28/2026
Reference Information
CVE: CVE-2026-48522, CVE-2026-48523, CVE-2026-48524, CVE-2026-48525