CVE-2023-37748
Description
ngiflib commit 5e7292 was discovered to contain an infinite loop via the function DecodeGifImg at ngiflib.c.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
An infinite loop vulnerability in ngiflib's DecodeGifImg function allows denial of service via a crafted GIF.
Vulnerability
An infinite loop vulnerability exists in the DecodeGifImg function at ngiflib.c:556 in ngiflib commit 5e7292. The affected code uses a for(;;) loop without proper exit conditions when processing specially crafted GIF images, leading to an infinite loop. The vulnerable version is commit 5e7292bfabbeeee8dca0bf4c9a77ff10c8e3bf28 as reported in the reference [1].
Exploitation
An attacker can trigger the infinite loop by providing a malicious GIF file as input to the gif2tga program compiled with -DNGIFLIB_NO_FILE and address sanitizer. The proof of concept provided reproduces the issue by running ./gif2tga -i ./poc2. No authentication or special network position is required; the attacker only needs to convince a user to process the crafted file [1].
Impact
Successful exploitation results in a denial of service condition: the program enters an infinite loop and becomes unresponsive, consuming CPU resources. No arbitrary code execution or privilege escalation is achieved. The impact is limited to availability [1].
Mitigation
As of the publication date, no official fix has been released in the repository. Users should monitor the vendor's repository for updates or patches. Until a fix is available, avoid processing untrusted GIF files with the affected version [1][2].
AI Insight generated on May 26, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
2- ngiflib/ngiflibdescription
- Range: = commit 5e7292
Patches
0No patches discovered yet.
Vulnerability mechanics
Root cause
"Missing exit condition in the LZW decoding loop allows malformed GIF input to cause an infinite loop."
Attack vector
An attacker crafts a malicious GIF file that triggers an infinite loop in the `DecodeGifImg` function at `ngiflib.c:556` [ref_id=1]. The loop iterates reading LZW codes via `GetGifWord`, but when the input is crafted such that neither the end-of-file code (`eof`) nor the pixel-count-zero condition (`npix==0`) is ever reached, the loop never returns [ref_id=1]. The attacker delivers the file to a victim who runs the `gif2tga` utility (or any program using ngiflib to decode GIFs), causing a denial of service (DoS) due to the infinite loop [ref_id=1].
Affected code
The infinite loop occurs in the `DecodeGifImg` function in `ngiflib.c` at line 556, within a `for(;;)` loop that processes LZW-encoded GIF image data [ref_id=1]. The loop lacks a proper exit condition when certain malformed input is encountered, causing it to spin indefinitely.
What the fix does
No patch is included in the bundle. The advisory [ref_id=1] reports the infinite loop at line 556 of `ngiflib.c` in the `DecodeGifImg` function but does not provide a fix. A proper remediation would add a maximum-iteration guard or additional input validation inside the `for(;;)` loop to break out when the decoder makes no progress after a reasonable number of iterations, preventing the hang on malformed GIF input.
Preconditions
- inputThe victim must run a program (e.g., gif2tga) that uses ngiflib to decode a GIF file supplied by the attacker.
- inputThe attacker must provide a specially crafted GIF file (poc2) that triggers the infinite loop in DecodeGifImg.
Reproduction
Clone the repository at commit 5e7292bfabbeeee8dca0bf4c9a77ff10c8e3bf28, build with `CC="clang -fsanitize=address -g" CFLAGS+=-DNGIFLIB_NO_FILE make`, then run `./gif2tga -i ./poc2` using the PoC file from https://github.com/GGb0ndQAQ/POC/blob/main/ngiflib/poc2 [ref_id=1].
Generated on May 26, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
1News mentions
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