CVE-2026-102559: A flaw was found in libsoup

Q: How do I fix CVE-2026-102559?

libsoup: upgrade to 3.7.3; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2026-102559 being exploited?

CVE-2026-102559 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-102559 affect?

CVE-2026-102559 affects libsoup, enterprise linux. Severity is high (CVSS 8.6). A flaw was found in libsoup. When constructing a masked WebSocket client frame for a very large outgoing payload, size values passed to GByteArray allocation APIs could be truncated while the masking routine still used the full length, caus

Q: How urgent is CVE-2026-102559?

Priority 49/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 8.6REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2026-102559 is a high-severity flaw (CVSS 8.6) affecting libsoup, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw was found in libsoup. When constructing a masked WebSocket client frame for a very large outgoing payload, size values passed to GByteArray allocation APIs could be truncated while the masking routine still used the full length, causing a heap buffer overflow.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.6 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 66%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-09-29
Last modified	2026-10-19

Publisher (CNA): Red Hat, Inc. · Vendor: gnome · redhat

Last updated 2026-10-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-29 18:17 UTCPublished CVE record published
2026-10-19 05:17 UTCUpdated Record last modified

gnome libsoup UPGRADE

Affected: < 3.7.3

Fixed in: 3.7.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libsoup || rpm -q libsoup || libsoup --version

2. UPGRADE to 3.7.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libsoup

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libsoup

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

redhat enterprise linux MITIGATE

Affected: 7.0 · 8.0 · 9.0 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Advisories and coverage

Official advisories

Amazon Linux 2023 ALAS: ALAS2023-2026-3212 (important): libsoup 2026-10-12
Amazon Linux 2 ALAS: ALAS2-2026-3998 (important): libsoup 2026-10-12

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-102559?

libsoup: upgrade to 3.7.3; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-102559 being exploited?

CVE-2026-102559 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-102559 affect?

CVE-2026-102559 affects libsoup, enterprise linux. Severity is high (CVSS 8.6). A flaw was found in libsoup. When constructing a masked WebSocket client frame for a very large outgoing payload, size values passed to GByteArray allocation APIs could be truncated while the masking routine still used the full length, caus

How urgent is CVE-2026-102559?

Priority 49/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Related CVEs

CVE-2026-2708 LOW 3.7 MITIGATE MITIGATE A request smuggling vulnerability exists in libsoup's HTTP/1 header parsing logic
CVE-2026-12548 MEDIUM 4.2 MITIGATE MITIGATE A heap out-of-bounds read flaw was found in libsoup
CVE-2026-102560 HIGH 8.6 UPGRADE MITIGATE A flaw was found in libsoup
CVE-2026-102558 HIGH 8.6 UPGRADE MITIGATE A flaw was found in libsoup
CVE-2026-102557 HIGH 8.6 UPGRADE MITIGATE A flaw was found in libsoup

References

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