CVE-2026-26740
Published: 18 March 2026
Summary
CVE-2026-26740 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Giflib Project Giflib. Its CVSS base score is 8.2 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 23.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SI-16 (Memory Protection) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-26740 is a buffer overflow vulnerability (CWE-787) affecting giflib version 5.2.2. The flaw resides in the EGifGCBToExtension function, which allows overwriting an existing Graphic Control Extension block without validating its allocated size, potentially leading to heap corruption. Published on 2026-03-18, it carries a CVSS v3.1 base score of 8.2 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H).
A remote attacker can exploit this vulnerability over the network with low attack complexity, requiring no privileges or user interaction. Exploitation triggers a denial of service through application crashes due to the unvalidated buffer overwrite, alongside limited integrity impacts such as potential data tampering, but no confidentiality loss.
A proof-of-concept demonstrating the heap out-of-bounds write via gce_len in giflib giftool is available at https://github.com/zakkanijia/POC/blob/main/giflib/giftool/giflib_giftool_gce_len_heap_oobwrite_disclosure.md. No official advisories or patches are detailed in the provided references.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-12914
Vulnerability details
Buffer Overflow vulnerability in giflib v.5.2.2 allows a remote attacker to cause a denial of service via the EGifGCBToExtension overwriting an existing Graphic Control Extension block without validating its allocated size.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote buffer overflow in giflib enables exploitation of public-facing applications (T1190) and application crashes via exploitation (T1499.004).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mitigates the buffer overflow in giflib by requiring timely remediation through patching or upgrading to a version that validates allocated size in EGifGCBToExtension.
Implements memory protection mechanisms such as address space layout randomization and data execution prevention that thwart exploitation of the heap buffer overflow leading to corruption and crashes.
Requires validation of GIF input sizes and structures before processing with giflib, reducing the risk of triggering the unvalidated overwrite in EGifGCBToExtension.