CVE-2024-52811 Acks not validated before logged to qlog leads to buffer overflow in ngtcp2
An integer underflow in ngtcp2's qlog logging leads to a heap buffer overflow, potentially allowing code execution or denial of service when qlog is enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-52811?
CVE-2024-52811 is a high-severity vulnerability in ngtcp2, published on 25 Nov 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The ngtcp2 project is an effort to implement IETF QUIC protocol in C. In affected versions acks are not validated before being written to the qlog leading to a buffer overflow. In `ngtcp2_conn::conn_recv_pkt` for an ACK, there was new logic that got added to skip `conn_recv_ack` if an ack has already been processed in the payload. However, this causes us to also skip `ngtcp2_pkt_validate_ack`. The ack which was skipped still got written to qlog. The bug occurs in `ngtcp2_qlog::write_ack_frame`. It is now possible to reach this code with an invalid ack, suppose `largest_ack=0` and `first_ack_range=15`. Subtracting `largest_ack - first_ack_range` will lead to an integer underflow which is 20 chars long. However, the ngtcp2 qlog code assumes the number written is a signed integer and only accounts for 19 characters of overhead (see `NGTCP2_QLOG_ACK_FRAME_RANGE_OVERHEAD`). Therefore, we overwrite the buffer causing a heap overflow. This is high priority and could potentially impact many users if they enable qlog. qlog is disabled by default. Due to its overhead, it is most likely used for debugging purpose, but the actual use is unknown. ngtcp2 v1.9.1 fixes the bug and users are advised to upgrade. Users unable to upgrade should not turn on qlog.
Weakness: CWE-670
Which versions are affected by CVE-2024-52811?
Linux distribution packages (1)
ngtcp2 openSUSE:Tumbleweed | All versions | 1.10.0-1.1 |
How do I fix CVE-2024-52811?
Upgrade to a fixed version.
Is CVE-2024-52811 being exploited?
There is no known exploitation of CVE-2024-52811 in the wild and no public exploit code.
Sources
Also known as GHSA-4gmv-gf46-r4g5, UBUNTU-CVE-2024-52811, openSUSE-SU-2025:14766-1.