CVE-2024-52811: 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 lea...

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.

Metrics

CVSS 3.1

8.2/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

EPSS Probability

0.80%

52.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-670

References

Timeline

Published: Nov 25, 2024
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2024-52811?

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.

How severe is CVE-2024-52811?

CVE-2024-52811 has a CVSS score of 8.2/10 (HIGH severity). The EPSS model estimates a 0.80% probability of exploitation in the next 30 days.

How do I fix CVE-2024-52811?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.