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How the CVE Works (Technical Details)
The vulnerability exists in Prometheus’s remote read endpoint (/api/v1/read). The endpoint does not properly validate the declared decoded length of an incoming snappy-compressed request body. A remote, unauthenticated attacker can exploit this by submitting a specially crafted snappy payload【1†L9-L11】. This malicious payload is small in size but declares an extremely large length after decompression. Upon receiving the request, the Prometheus server allocates heap memory based on the declared decoded size, not the actual data size【1†L9-L10】. This leads to a massive per-request memory allocation. Under a concurrent load, these allocations quickly consume all available memory, resulting in memory exhaustion and a crash of the entire Prometheus process【1†L11】. The crash causes a complete denial-of-service, effectively taking the monitoring system offline. The issue is particularly dangerous because it is triggered by the server endpoint that typically expects read queries, and it does not require any prior authentication to exploit【1†L10】.
DailyCVE Form
Platform: Prometheus
Version: < 3.11.3,<3.5.3
Vulnerability : Remote DoS
Severity: High
Date: 2026-05-04
Prediction: 2026-05-15
Analytics
What Undercode Say:
Simulate the malicious snappy payload using python
WARNING: For educational purposes only.
import snappy
import struct
Craft a header that claims a huge uncompressed size
fake_header = struct.pack('<I', 0x7fffffff) Declare max 2GB size
Actual compressed data (none, empty)
payload = fake_header
Send request to vulnerable Prometheus
curl -X POST http://target:9090/api/v1/read \
-H "Content-Type: application/x-snappy-framed" \
--data-binary @payload
Exploit:
An attacker sends a POST request to `/api/v1/read` with a crafted header. The header lies about the decoded length. The server tries to allocate that memory and crashes.
Protection from this CVE
– Upgrade to Prometheus versions 3.11.3, 3.5.3, or any later release【1†L17-L19】.
– As a workaround, place Prometheus behind a reverse proxy or firewall that requires authentication before routing requests to the `/api/v1/read` endpoint【1†L21-L22】.
Impact
– Denial of service (crash) of the Prometheus server.
– Complete loss of monitoring and alerting capabilities until manual restart.
– Unauthenticated exploitation, remotely exploitable over the network.
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Sources:
Reported By: github.com
Extra Source Hub:
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