CVE-2026-102559: Libsoup2.4 · A flaw was found in libsoup
Affects libsoup2.4Source GCVE Database
Not known to be exploited · CVSS 8.6 High.
Data as of 3 Nov 2026, 22:58 UTC
Thin evidence
One scorer or none| CNA (redhat) | CVSS 3.1 | 8.6 |
|---|
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:HExploitation evidence
Disclosed: evidence found.
CVE published 29 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 3 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10libsoup2.4pkg:deb/ubuntu/libsoup2.4?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10libsoup3pkg:deb/ubuntu/libsoup3?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlibsoup3pkg:deb/ubuntu/libsoup3?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu Pro 26.04 LTSlibsoup2.4pkg:deb/ubuntu/libsoup2.4?arch=source&distro=esm-apps/resoluteOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlibsoup2.4pkg:deb/ubuntu/libsoup2.4?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlibsoup3pkg:deb/ubuntu/libsoup3?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
The recommended mitigation is to enforce application-level limits on outgoing WebSocket message sizes to prevent sending extremely large messages. Avoid sending untrusted bulk data as a single WebSocket message. Monitor vendor advisories for patch availability.
Description
A heap buffer overflow vulnerability exists in libsoup 2.4 when constructing a masked WebSocket client frame for very large outgoing payloads. The flaw arises because size values passed to GByteArray allocation APIs can be truncated, while the masking routine uses the full length, leading to heap corruption or denial of service in the sending process. Triggering this requires sending an extremely large WebSocket message, which may be attacker-influenced if application-level message size limits are not enforced.
References
- ubuntu.com/security/CVE-2026-102559 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-102559 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543285 (opens in a new tab)
- gitlab.gnome.org/GNOME/libsoup/-/work_items/554 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-102559 (opens in a new tab)