CVE-2025-9820

A flaw was found in the GnuTLS library, specifically in the gnutls_pkcs11_token_init() function that handles PKCS#11 token initialization. When a token label longer than expected is processed, the function writes past the end of a fixed-size stack buffer. This programming error can cause the application using GnuTLS to crash or, in certain conditions, be exploited for code execution. As a result, systems or applications relying on GnuTLS may be vulnerable to a denial of service or local privilege escalation attacks.

Weakness

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

Affected Software

Name	Vendor	Start Version	End Version
Red Hat Enterprise Linux 10	RedHat	gnutls-0:3.8.10-3.el10_1	*
Red Hat Enterprise Linux 9	RedHat	gnutls-0:3.8.3-10.el9_7	*
Red Hat Enterprise Linux 9	RedHat	gnutls-0:3.8.3-10.el9_7	*
Red Hat Insights proxy 1.5	RedHat	insights-proxy/insights-proxy-container-rhel9:sha256:325c34e2506d715975171557d40afb449c79cf6e0c41b35760977d5cafb827b8	*
Red Hat Update Infrastructure 5	RedHat	rhui5/cds-rhel9:sha256:200c27e9b396276bd505c6b41127ac5eb1d94d620172cb818ae733f2a21ac524	*
Red Hat Update Infrastructure 5	RedHat	rhui5/haproxy-rhel9:sha256:d98fd3fe5f5f9acd0efae7db19b61b864be1eb2fbe2586a1b6be2429fa2cc7a3	*
Red Hat Update Infrastructure 5	RedHat	rhui5/installer-rhel9:sha256:2c50c87906a1abebf427a70f401c409f1258cb55d2096f517db870ec991cfd7f	*
Red Hat Update Infrastructure 5	RedHat	rhui5/rhua-rhel9:sha256:5f1fbf66fb349a7baf066a1216d39989c3b89f18ec5108b96d9643baf4856778	*
Gnutls28	Ubuntu	devel	*
Gnutls28	Ubuntu	fips-updates/jammy	*
Gnutls28	Ubuntu	fips-updates/noble	*
Gnutls28	Ubuntu	jammy	*
Gnutls28	Ubuntu	noble	*
Gnutls28	Ubuntu	plucky	*
Gnutls28	Ubuntu	questing	*
Gnutls28	Ubuntu	upstream	*

Potential Mitigations

Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

NVD	https://nvd.nist.gov/vuln/detail/CVE-2025-9820
CWE	https://cwe.mitre.org/data/definitions/121.html

Stack-based Buffer Overflow

Weakness

Affected Software

Potential Mitigations

References