Quick answers
- Is CVE-2026-75421 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-75421 being exploited in the wild.
- How severe is CVE-2026-75421?
- Medium severity, with a CVSS score of 4, published 25 August 2026.
- Which products and versions are affected?
- Aria2 <=1.37.0.
- Is there a fix for CVE-2026-75421?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-75421 attacked?
- It is attacked with local access.
- Am I affected by CVE-2026-75421?
- Check whether you run Aria2 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is a stack-buffer-underflow in the IOFile::getLine() function that occurs during parsing of URI list files. When aria2 processes a specially crafted input file via the -i flag, the getLine() function attempts to read from a stack buffer at an offset that underflows the allocated region, as confirmed by AddressSanitizer detection. The vulnerability is triggered during the URI list parsing phase in download_helper.cc without requiring authentication or special network access—only a maliciously crafted local file is needed. An attacker can exploit this to trigger a denial of service (crash) or potentially achieve code execution. A patch has been proposed via pull request #2376.
Affected products
- aria2 aria2 <=1.37.0
Timeline
- 2026-08-07: disclosed: Issue opened on GitHub
- 2026-08-25: advisory: CVE-2026-75421 published